compositor-worker: Add CompositorProxyClient worker client of CompositorWorker.

third_party/WebKit/Source/core/page/ChromeClient.h

Index: third_party/WebKit/Source/core/page/ChromeClient.h
diff --git a/third_party/WebKit/Source/core/page/ChromeClient.h b/third_party/WebKit/Source/core/page/ChromeClient.h
index 2fbe9321c3fee26b32e4b94913affab1d4d814c2..a1e634f40e16ab05bdec36bc28026eeb1a0e013a 100644
--- a/third_party/WebKit/Source/core/page/ChromeClient.h
+++ b/third_party/WebKit/Source/core/page/ChromeClient.h
@@ -48,6 +48,7 @@ class AXObject;
 class ColorChooser;
 class ColorChooserClient;
 class CompositorAnimationTimeline;
+class CompositorProxyClient;
 class DateTimeChooser;
 class DateTimeChooserClient;
 class Element;
@@ -269,6 +270,8 @@ public:
     virtual void registerPopupOpeningObserver(PopupOpeningObserver*) = 0;
     virtual void unregisterPopupOpeningObserver(PopupOpeningObserver*) = 0;
 
+    virtual CompositorProxyClient* createCompositorProxyClient() = 0;
+
     virtual FloatSize elasticOverscroll() const { return FloatSize(); }
 
     // Called when observed XHR, fetch, and other fetch request with non-GET